1. Field of the Invention
This invention relates to an image forming apparatus.
2. Background of Related Art
Image forming apparatuses such as printers, facsimile machines, and photocopiers, inter alia printers, in prior art are provided with such as, e.g., image forming units, LED (Light Emitting Diode) heads serving as exposure devices, transfer rollers, fixing devices, and paper cassettes. The image forming units are disposed detachably to the printer body or the apparatus body, being equipped with such as, e.g., photosensitive drums, charge rollers, developing rollers, developing blades, toner supply rollers, cleaning blades, and toner cartridges. Toners are contained in the toner cartridges, respectively, and paper is contained in the respective paper cassettes.
In such an image forming unit, the LED head exposes a surface of the photosensitive drum charged uniformly with the charge roller to form electrostatic latent images. The toner supplied in the image forming unit body from the toner cartridge is further supplied to the developing roller with a toner supply roller, thereby forming a thin toner layer on the developing roller by the developing blade. The toner on the developing roller is attached to the electrostatic latent images on the photosensitive drums to form toner images on the photosensitive drums by developing the electrostatic latent images.
The paper fed out from the paper cassette is conveyed between the photosensitive drum and the transfer roller, and the toner image is transferred onto the paper with the transfer roller. The paper is fed to the fixing device, and the toner image is fixed to the paper at the fixing device. The images are thus formed, and the paper subject to printing is ejected from the apparatus body.
The LED head includes such as, e.g., a substrate, an LED array made of plural LED elements and attached to the substrate in extending in an axial direction of the photosensitive drum, and lens arranged between the LED array and the photosensitive drum in extending in an axial direction of the photosensitive drum. Where the LED head is driven and where the respective LED elements are selectively emitted, the respective rays according to light emission are focused by the lens to form the electrostatic latent images upon radiation to the surface of the photosensitive drum (see, e.g., Japanese Patent Application Publication No. 2011-88,384 (A1)).
With the prior art printer, however, the toner may attach to the LED head to make the lens surface dusty during the printing operation, so that electrostatic latent images may not be formed accurately where rays according to the LED elements' light emissions are not radiated properly onto the surface of the photosensitive drum, and so that the printer may resultantly suffer from inferior image quality.
It is an object of the invention to provide an image forming apparatus solving above problems on prior art printers, being capable of cleaning the exposure device of the image forming apparatus, and preventing the image quality of the image forming apparatus from becoming inferior.